From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3EBDFC47088 for ; Wed, 26 May 2021 22:45:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0BDE7613D2 for ; Wed, 26 May 2021 22:45:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234550AbhEZWq4 (ORCPT ); Wed, 26 May 2021 18:46:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:56300 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234099AbhEZWqz (ORCPT ); Wed, 26 May 2021 18:46:55 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A06916108B; Wed, 26 May 2021 22:45:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1622069122; bh=6ujNqtW7df/mjKvrDRHDhRrKax2FzQXVHxjjLMdf46g=; h=Date:From:To:Subject:From; b=x4wpAvwyGMXI5+PBI9qqlRZsxgUy7Re6+svf40to/uzuH21jm1hIcITU61J20fdYl PbC1eaUYyykoeWQoUfFA0Mcf4r2DuUUkmlVQ+ZWD4cROdPPQbVLbUPMK877A7MMYf8 ExkCrP/9Fp+VHXmQ7DOKRHRzw+UhyEHBcQfNLtb0= Date: Wed, 26 May 2021 15:45:22 -0700 From: akpm@linux-foundation.org To: hughd@google.com, mm-commits@vger.kernel.org, shy828301@gmail.com, ziy@nvidia.com Subject: + mm-thp-replace-debug_vm-bug-with-vm_warn-when-unmap-fails-for-split.patch added to -mm tree Message-ID: <20210526224522.-PA7kuGmM%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split has been added to the -mm tree. Its filename is mm-thp-replace-debug_vm-bug-with-vm_warn-when-unmap-fails-for-split.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-thp-replace-debug_vm-bug-with-vm_warn-when-unmap-fails-for-split.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-replace-debug_vm-bug-with-vm_warn-when-unmap-fails-for-split.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Yang Shi Subject: mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split When debugging the bug reported by Wang Yugui [1], try_to_unmap() may fail, but the first VM_BUG_ON_PAGE() just checks page_mapcount() however it may miss the failure when head page is unmapped but other subpage is mapped. Then the second DEBUG_VM BUG() that check total mapcount would catch it. This may incur some confusion. And this is not a fatal issue, so consolidate the two DEBUG_VM checks into one VM_WARN_ON_ONCE_PAGE(). [1] https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tec= h.com/ Link: https://lkml.kernel.org/r/20210526201239.3351-1-shy828301@gmail.com Signed-off-by: Yang Shi Reviewed-by: Zi Yan Acked-by: Hugh Dickins Signed-off-by: Andrew Morton --- mm/huge_memory.c | 29 +++++++++-------------------- 1 file changed, 9 insertions(+), 20 deletions(-) --- a/mm/huge_memory.c~mm-thp-replace-debug_vm-bug-with-vm_warn-when-unmap-fails-for-split +++ a/mm/huge_memory.c @@ -2300,21 +2300,20 @@ void vma_adjust_trans_huge(struct vm_are static void unmap_page(struct page *page) { enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD; - bool unmap_success; VM_BUG_ON_PAGE(!PageHead(page), page); - if (PageAnon(page)) + if (PageAnon(page)) { try_to_migrate(page, ttu_flags); - else + } else { /* * Don't install migration entries for file backed pages. This * helps handle cases when i_size is in the middle of the page * as there is no need to unmap pages beyond i_size manually. */ - unmap_success = try_to_unmap(page, ttu_flags | - TTU_IGNORE_MLOCK); - VM_BUG_ON_PAGE(!unmap_success, page); + try_to_unmap(page, ttu_flags | TTU_IGNORE_MLOCK); + } + VM_WARN_ON_ONCE_PAGE(page_mapped(page), page); } static void remap_page(struct page *page, unsigned int nr) @@ -2625,7 +2624,7 @@ int split_huge_page_to_list(struct page struct deferred_split *ds_queue = get_deferred_split_queue(head); struct anon_vma *anon_vma = NULL; struct address_space *mapping = NULL; - int count, mapcount, extra_pins, ret; + int extra_pins, ret; pgoff_t end; VM_BUG_ON_PAGE(is_huge_zero_page(head), head); @@ -2684,7 +2683,6 @@ int split_huge_page_to_list(struct page } unmap_page(head); - VM_BUG_ON_PAGE(compound_mapcount(head), head); /* block interrupt reentry in xa_lock and spinlock */ local_irq_disable(); @@ -2702,9 +2700,7 @@ int split_huge_page_to_list(struct page /* Prevent deferred_split_scan() touching ->_refcount */ spin_lock(&ds_queue->split_queue_lock); - count = page_count(head); - mapcount = total_mapcount(head); - if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) { + if (page_ref_freeze(head, 1 + extra_pins)) { if (!list_empty(page_deferred_list(head))) { ds_queue->split_queue_len--; list_del(page_deferred_list(head)); @@ -2724,16 +2720,9 @@ int split_huge_page_to_list(struct page __split_huge_page(page, list, end); ret = 0; } else { - if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { - pr_alert("total_mapcount: %u, page_count(): %u\n", - mapcount, count); - if (PageTail(page)) - dump_page(head, NULL); - dump_page(page, "total_mapcount(head) > 0"); - BUG(); - } spin_unlock(&ds_queue->split_queue_lock); -fail: if (mapping) +fail: + if (mapping) xa_unlock(&mapping->i_pages); local_irq_enable(); remap_page(head, thp_nr_pages(head)); _ Patches currently in -mm which might be from shy828301@gmail.com are mm-memory-add-orig_pmd-to-struct-vm_fault.patch mm-memory-make-numa_migrate_prep-non-static.patch mm-thp-refactor-numa-fault-handling.patch mm-migrate-account-thp-numa-migration-counters-correctly.patch mm-migrate-dont-split-thp-for-misplaced-numa-page.patch mm-migrate-check-mapcount-for-thp-instead-of-refcount.patch mm-thp-skip-make-pmd-prot_none-if-thp-migration-is-not-supported.patch mm-thp-replace-debug_vm-bug-with-vm_warn-when-unmap-fails-for-split.patch mm-rmap-make-try_to_unmap-void-function.patch